1. Field of the Invention
The present invention relates to a semiconductor process. More particularly, the present invention relates to a method for forming a patterned photoresist layer.
2. Description of Related Art
Pressed by the growing requirements on circuit integration, the size of circuit devices is designed to be smaller and smaller. In the whole semiconductor process, photolithography process is the most important. Those relevant to the structure of a metal-oxide-semiconductor (MOS) device, for example, patterns of thin films, and regions doped with dopants, are determined by the photolithography step. Furthermore, whether the device integration of the entire semiconductor industry can be developed toward to obtain a smaller line width is also determined by the development of photolithography process technology.
However, during the implantation process, oil and gas or free radicals in the reaction chamber will be polymerized to form polymer contaminants on the surface of a wafer due to the bombardment of the implanted ions. Thus, during the photolithography process following the implantation process to form a patterned photoresist on the wafer, the formed photoresist layer may have dopants caused by the residual contaminants on the surface of the wafer. As a result, after patterning the photoresist, the pattern transferred from the mask to the photoresist is deformed. Therefore, the devices produced subsequently have defects, which will result in undesirable electrical performance, and thus reduce the product yield.